Monitoring camera apparatuses are widely used, and monitoring camera apparatuses not only for indoor use but also for outdoor use have been provided. Further, in addition to the conventional box-type monitoring camera apparatuses, domed monitoring camera apparatuses have recently been spreading.
The monitoring camera apparatus has a focus adjustment function of performing focus adjustment by moving the imaging device in an optical axis direction. Such focus adjustment performed by moving an imaging device is called “back-focus adjustment”. A technique of automatically performing back-focus adjustment has also been proposed. This technique has been disclosed, for example, in Japanese Patent Laid-Open No. 2006-148299. Hereinafter, the automatic back-focus adjustment function is referred to as “focus adjustment function”. The focus adjustment function reduces image blurring in the following scenes.
The monitoring camera apparatus, used day and night, has a function of automatically performing switching between a color mode for daytime and a monochrome mode for nighttime. This function is called “day and night function”, for example. In the color mode for daytime, an infrared cutoff filter is placed in front of the imaging device. However, in the monochrome mode for nighttime, the infrared cutoff filter is removed, as a result, the average wavelength of incident light shifts. Further, in the case that infrared illumination is provided, the illumination wavelength also shifts. When the wavelength shifts, the focus position changes because of chromatic aberration of lens. Thus, in order to reduce the blurring caused by the focus position shift, focus adjustment is performed by the focus adjustment function at the time of mode switching.
The focus adjustment function is also useful in the installation operation and adjustment operation for the domed monitoring camera apparatus. In the domed monitoring camera apparatus, the lens is covered by a semispherical dome cover. For example, assume that the monitoring camera apparatus includes a varifocal lens (variable focus lens). In this case, in installing the camera, the zoom ring and focus ring of the exposed lens are manually turned with the dome cover removed, so that zoom (field angle) and focus adjustment are performed. When the adjustment operation is completed, the dome cover is mounted. In such case, since the semispherical dome cover has optical performance, the focus position may shift so that blurring occurs. Thus, in order to reduce such blurring, focus adjustment is performed by the focus adjustment function.
The focus adjustment function can be automatically started by using the filter removal as a trigger at the time of switching between the color mode and monochrome mode. However, at the time of mounting the dome cover, the focus adjustment function cannot be automatically started. Thus it is needed to provide a constitution for generating a trigger for starting the focus adjustment function at the time of mounting the dome cover.
To satisfy the above demand, the conventional monitoring camera apparatus includes an external switch on an external surface of housing for starting the focus adjustment function. The dome cover is mounted and then the external switch is operated, so that focus adjustment is performed. The reason for installing the switch on the external surface is that the switch must be operated after mounting the cover.
Further, a controller apparatus may be connected to the monitoring camera apparatus. In this case, a trigger for starting the focus adjustment function can be generated by using the controller. For example, a small-sized controller is connected via a cable to the monitoring camera apparatus. Then, a menu screen is opened on the controller, and an instruction for focus adjustment is inputted as a trigger.
In the conventional monitoring camera apparatus for indoor use not requiring waterproofness, the external switch for starting focus adjustment can be installed. However, in the monitoring camera apparatus for outdoor use, the external switch is disadvantageous for ensuring waterproofness. Further, the external switch is disadvantageous in terms of appearance. When the external switch cannot be installed, focus adjustment cannot be performed at the time of mounting the cover.
If the external controller apparatus described above can be connected, focus adjustment can be started without installing the external switch. However, generally, the external controller is provided for the user separately from the monitoring camera apparatus. Not all users have the external controller. It is rather appropriate to say that many users don't have the external controller. In view of the above, it is desirable that the monitoring camera apparatus achieve required functions while the external controller is not connected. Focus adjustment is included in such required functions. Thus, even in a case where the external controller can be connected to the monitoring camera apparatus, there is a need to provide a constitution for starting focus adjustment function without using the external controller.
The above described problem is noticeable for vandal-proof monitoring camera apparatuses. The vandal-proof monitoring camera apparatuses have robustness for protection against breakage. In this case, robustness is implemented by increasing the wall thickness of cover; and since a thick cover is provided, the variation in optical path length increases, so the above described problem becomes noticeable.